1. Field of the Invention
Embodiments of the invention relate generally to the field of computer systems and interconnect fabrics.
2. Discussion of the Related Art
Many computer operations require the knowledge of which operation started or ended before another operation. One way this can be accomplished in a single computer system is by a simple counter in memory that is protected by a lock so that only one process can read and update the counter at a time. By checking the value that a process has received from this counter you can determine by a simple compare when process accessed the counter first.
However in a multi-computer system this can become problematic in that the counter usually is kept in a single system's memory and a request has to go all the way through the interface and operating system in order to request an update.
Another solution to this problem involves specialized hardware that resides on the network and responds with a transaction identifier (TID) when read. The issue with this solution is that the hardware device becomes a single point of failure. So in order to be highly available a secondary device on a different path is required that needs to 1) monitor the traffic to the current master and 2) detect the failure of the primary device. This sort of solution can result in a doubling of the traffic needed to simply satisfy the base requests.
Another method tries to address this problem by placing additional hardware into the controllers that attach to the host. The issue with this solution is that in implementation there needs to be a master and student situation where the students somehow monitor the master and take over in the event of a failure.